Vehicle used by child of Unionist leader (6)

I believe the answer is:

carson

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'unionist leader' is the definition.
The definition suggests a singular noun which matches the answer.

'vehicle used by child' is the wordplay.
'vehicle' becomes 'car' (car is a kind of vehicle).
'used by' is a charade indicator (letters next to each other).
'child' becomes 'son' (male child).
'car'+'son'='CARSON'

'of' is the link.

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I've seen this clue in The Irish Times.

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